Sick Kribensis- Help

[LimpingFish]

First of all- i'm sorry about my English.
About a month and a half ago i bought 2 Kribs, both males.
The first one, got himself hidden on the first second he got into the tank.
I saw him for few seconds everyday for about a week. Every day i saw him, his condition got worse. He was breathing heavily, he opened and closed his mouth, and his gills were working at high speed. I thought it might have been stress. He died at the end of the week.

The time has passed, and the second krib was living happily (so it seemed). He wasn't afraid, came to the glass of the tank when i was near, and seemed healthy.
One week ago, he started to hide, too. When i saw him, he started to get the same symptoms as the first krib- Hardly breath. 2 days later, he had more confidence, though his condition got worse. He sits on a place somewhere on the gravel, gasping , opening and closing widely his mouth and gills. His fins are streched, his colors got stronger, and his belly got deep-red color.

For the past 2 days i added a bit salt (i can't add more, because i have lots of cat-fish in the tank) and replaced about 15%-20% water every day.
I checked the water parameters too, and it went fine.
There is plenty of oxygen and plants, no co2 injection, and the filter is working very well.

No one that i asked knows what does my krib has, or what to do. If anyone has any idea what might be causing this, what is this disease, or what can i do in order to help him, please reply..
Thank you.

 

[semper fi]

have you used any kind of chemicals around the tank that may have inadvertently gotten in. say glass cleaner or any type of spray? air freshner?how long has this tank been set up and exactly what were the parameters? did you test the water? it is very important to not only check the water in the tank, but also the replacement water. what equipment do you have in the tank, ie heaters, aerator, powerheads, etc. what is the temp at?

i would add salt to the tank. one well rounded tablespoon for every five gallons of water. dissolve the correct amount in a cup of tank water and then add into the tank. do water changes of about 10% every night. add only salt to the amount of replacement water.

 

[LimpingFish]

Thank you for the reply.
I checked the water when the two kribs arrived, and the ammonia was zero, the nitrate and everything else was fine too, i don't remember the results. I will check the water again, tommorrow. The replacement water are fine, too.
I haven't used any chemicals near the tank, or in my room. By the way, if the water parameters were bad, all the fish would've suffer.. But it happens only to the kribs..
I got one 150 watt heater, the filter's clean water are coming above the tank, so it makes alot of bubbles (this is where the tank get most of its oxygen).
I have one thermometer. These are all the man-used objects that are inside the tank.
The temp is 28.
I added a bit of salt, but i can't add any more, as i have lots of cat-fish in the tank.
I do replace about 15% of water everyday now.


thanks.